1. Field
Embodiments of the present invention generally relate a substrate processing system and related substrate process, such as an etching/deposition process. More particularly, embodiments of the present invention relate to method and apparatus for providing processing gases to a process chamber with improved plasma dissociation efficiency.
2. Description of the Related Art
The fabrication of microelectronic devices includes a number of different stages, each including a variety of processes. During one stage, a particular process may include imparting a plasma to the surface of a substrate, such as a silicon substrate, to alter the physical and material properties of the substrate. This process may be known as etching, which may involve the removal of materials to form holes, vias, and/or other openings (referred to herein as “trenches”) in the substrate.
Plasma etch reactors are commonly used for etching trenches in semiconductor substrates. These reactors contain a chamber within which the substrate is supported. At least one reactive gas is supplied to the chamber and a radio frequency signal is coupled to the reactive gas to form the plasma. The plasma etches the substrate that is positioned within the reactor. The substrate may also be coupled to a radio frequency signal to bias the substrate during the etching process to enhance etching performance and trench profile.
These trench profiles often require different critical dimensions. The critical dimensions include width, depth, aspect ratio, resist selectivity, roughness of the sidewalls, and planarity of the sidewalls. These critical dimensions may be controlled by various factors, two of which are etching time and etching rate, which further depend on the materials being etched and the type of etching system being used.
One material of particular importance is silicon. Through silicon via (“TSV”) etching is a unique application that requires a low frequency bias and a low temperature environment to form deep trenches in a silicon substrate. However, during fabrication, the silicon is generally covered by multiple layers of other materials, such as an oxide layer and a metal layer that are deposited on the silicon. Oxides and metals include different etching requirements than that of silicon, such as a high frequency bias. In addition, during the deposition process, a thin film polymer layer may be deposited onto the layers of the substrate as the trench is being formed to protect the trench sidewalls prior to the etching process. This polymer layer may further include different etching requirements than the oxide, metal, or silicon layers. These distinct requirements influence and increase the complexity of the type of etching system used.
One type of etching system may include in situ plasma etching. Using this first type of etching system, a trench can be formed by alternating the removal and deposition of material on a substrate in a single reactor with a removing plasma and a deposition plasma. Another type of etching system may include remote plasma etching. Using this second type of etching system, a trench can be formed as in the in situ system, except that the plasmas may be generated in a remote reactor prior to being introduced onto the substrate located in the primary reactor. In addition to, the types of etching systems, the process of etching with each system may also vary. Some etching processes employ multi-process approaches, such as a time multiplexed gas modulation (“TMGM”) system or a Bosch system, that includes several recipe processes, such as etch and deposition process, or etch, flash, and deposition processes. The TMGM process etches a material for a period of time and then deposits a protective film upon the previously etched surface to protect the surface, typically the sidewalls of the trench, from further etching. These two processes are repeated as a deeper and deeper trench is formed. The different types of etching systems and processes has particular advantages and disadvantages when forming different trench profiles in different material layers.
The material etch rate in an etching system is often a function of source power. Higher etch rates can be achieved with higher source powers because higher source powers lead to higher dissociation rate of processing gases.
Embodiments of the present invention increase etch rate by obtaining higher dissociation rate of processing gases without increasing source power, therefore, increase efficiency of an etch system.